//  PermutationUtility.cpp
//
//  Author:
//       Esteban López-Camacho <esteban@lcc.uma.es>
//
//  Copyright (c) 2011 Antonio J. Nebro, Juan J. Durillo
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include <PermutationUtility.h>

int * PermutationUtility::intPermutation(int length) {

  int * aux    = new int[length];
  int * result = new int[length];

  // First, create an array from 0 to length - 1.
  // Also is needed to create an random array of size length
  for (int i = 0; i < length; i++) {
    result[i] = i;
    aux[i] = PseudoRandom::randInt(0,length-1);
  } // for

  // Sort the random array with effect in result, and then we obtain a
  // permutation array between 0 and length - 1
  for (int i = 0; i < length; i++) {
    for (int j = i + 1; j < length; j++) {
      if (aux[i] > aux[j]) {
        int tmp;
        tmp = aux[i];
        aux[i] = aux[j];
        aux[j] = tmp;
        tmp = result[i];
        result[i] = result[j];
        result[j] = tmp;
      } // if
    } // for
  } // for
  delete[] aux;

  return result;

}
